(1) Field of the Invention
The invention is related to an electrical powered tail rotor of a helicopter with the features of the preamble of claim 1.
(2) Description of Related Art
The power consumed by a tail rotor of state of the art helicopters is supplied from a central energy generator via a main gear box, a plurality of intermediate gears and a tail rotor shaft. By removing the main gear box and the rigid mechanical coupling between energy generator and tail rotor more design flexibility for the helicopter may be attained. One of the keys to realise an electrical powered tail rotor of a helicopter is a suitable electrical motor.
The document US 2004051401 A1 discloses an electric motor for rotating an object around a central axis. The electric motor includes a motor casing. A circular segmented rail element is disposed within the motor casing about the central axis. The circular segmented rail element includes metallic non-ferrous segments interleaved with non-metallic segments. Each of the metallic non-ferrous segments has a predetermined segment length. At least one coil element is connected to the motor casing. The circular segmented rail element is disposed adjacent the at least one coil element. The at least one coil element has a predetermined coil length that is less than or equal to the predetermined segment length. The at least one-coil element is configured to apply electromagnetic energy to the circular segmented rail element, such that the circular segmented rail element rotates around the central axis.
The document WO 0184063 A2 discloses a stator assembly for a brushless DC ring motor for a cooling fan piloted on the stator assembly. A ring supports a plurality of fan blades for sweeping an area inside the shroud. A rotor assembly for the brushless DC ring motor is attached to the ring of the cooling fan. The rotor assembly confronts the stator assembly around an outer diameter of the stator assembly. The cooling system is controlled by an electronic controller to rotate the cooling fan to provide appropriate cooling for the vehicle.
A hybrid helicopter drive has been proposed in the document “The Hybrid Helicopter Drive, . . . ” by Peter Jänker et al. at Europ. Rotorcraft Forum, September 2010” with an integration of an electrical motor for a Fenestron tail rotor. The electrical motor is realised by so called disc shaped electrical “Trans-Flux-Motors” with increased pole numbers. The electrical “Trans-Flux-Motor” for the Fenestron tail rotor is conceived as a torus around the Fenestron opening, the blade tips of the tail rotor being fixed to its rotating component. An electrical “Trans-Flux-Motor” is presented in document DE 10 2007 013 732 A1.
The document DE 102007013732 A1 discloses a direct drive with a stator and one or multiple support rings 3 that are made of plastic. The support rings supports the permanent magnets that are arranged in two or more concentric rings. The annular or sector shaped stator logs, made of plastic, are arranged in axial direction adjacent to the concentric rings of the support rings in such a way that a magnetic flux is allowed in radial direction between adjacent concentric rings.
The document “The Hybrid Helicopter Drive, . . . ” by Peter Jänker et al. at Europ. Rotorcraft Forum, September 2010” further discloses such electrical “Trans-Flux-Motors” with two disks for the main rotor.
The document WO 2005/100154 A1 discloses a rotor for mounting on a helicopter drive shaft, comprising a hub for location on the shaft and a plurality of blades mounted to and extending out from the hub, wherein a pitch angle ([phi]) of at least one of the blades is controllable with respect to each other blade by an electrical stepper motor mechanism arranged at the hub. Also disclosed is a method for determining a pitch angle ([phi]) of the blades of the rotor, a computer program arranged to, when loaded onto a computing system, utilise an algorithm for determining blade pitch angle ([phi]) values for the blades, an alternator for providing power to motors that control the pitch of the blades and a control method for implementation by a computer in controlling the pitch of the blades in real time.
The document US 2009/140095 A1 discloses a rotary-wing aircraft with an electric motor mounted along an axis of rotation to drive a rotor system about the axis of rotation.
The document U.S. Pat. No. 4,953,811 A discloses a helicopter engine turning a tail rotor while it is turning the main rotor. Tail rotors, while essential components, take power from the engine, introduce a drag force, add weight, and increase rotor noise. Since the engine is as close as possible to the main rotor, the complexity, number of parts, weight and efficiency of the remote tail rotor have gone unchanged. Those parts and hence their added weights have been eliminated. A self-driving tail rotor for a helicopter is provided.
The document WO 2009/129309 A2 discloses a wind generator in which superconducting ring generators are utilized without the need for a load bearing drive shaft and other mechanical components allowing for the use of variable geometry blades, a decrease in the overall weight, and an increase in the overall efficiency of the wind generator system.
The document US 2006/049304 A1 discloses a hover aircraft with an air impeller engine having an air channel duct and a rotor with outer ends of its blades fixed to an annular impeller disk that is driven by magnetic induction elements arrayed in the air channel duct. The air-impeller engine is arranged vertically in the aircraft frame to provide vertical thrust for vertical takeoff and landing. Preferably, the air-impeller engine employs dual, coaxial, contra-rotating rotors for increased thrust and gyroscopic stability. An air vane assembly directs a portion of the air thrust output at a desired angle to provide a horizontal thrust component for flight maneuvering or translation movement. The aircraft can employ a single engine in an annular fuselage, two engines on a longitudinal fuselage chassis, three engines in a triangular arrangement for forward flight stability, or other multiple engine arrangements in a symmetric, balanced configuration. Other flight control mechanisms may be employed, including side winglets, an overhead wing, and/or air rudders or flaps. An integrated flight control system can be used to operate the various flight control mechanisms. Electric power is supplied to the magnetic induction drives by high-capacity lightweight batteries or fuel cells. The hover aircraft is especially well suited for applications requiring VTOL deployment, hover operation for quiet surveillance, maneuvering in close air spaces, and long duration flights for continuous surveillance of ground targets and important facilities requiring constant monitoring.